This invention relates generally to an engine control system for a marine propulsion device, and particularly to an engine control system which is adapted to protect a two-cycle outboard motor.
With two-cycle internal combustion engines, it has been the general practice to lubricate the engine by mixing lubricating oil with the fuel mixture. Although such arrangements offer extreme simplicity, the mixing of lubricating oil with the fuel can be troublesome to the user of the engine. In addition, the requirement for mixing lubricant with the fuel and lubricating the components of the engine with the fuel/air mixture does not always insure the adequate amount of lubrication to the various components to be lubricated under all running conditions. In order to obviate some of these difficulties, it has been proposed to provide a lubricating system where the lubricant is contained within a separate tank from the fuel and is supplied to the engine during its running. Such arrangements have a number of advantages. One such separate lubrication system is described in the commonly assigned co-pending U.S. patent application Ser. No. 610,847, entitled "Separate Lubricating System For Marine Propulsion Device", which is hereby incorporated by reference.
When the engine in question constitutes the power unit of an outboard motor, however, the provision of such separate lubricating systems can give rise to certain practical difficulties. For example, when the lubricant in the storage tank or reservoir reaches a low level, it is desirable to run the outboard motor at a low speed which will conserve the supply of the lubricant and prevent the engine from running at a high speed when the supply of lubricant is depleted. Thus, it would be desirable to provide a protection system for the engine which will regulate the speed of the engine so as to reduce the engine speed to a predetermined low level. Such a protection system would override the particular engine throttle setting which may be set for a higher engine speed. It would also be desirable for the protection system to provide a perceptible output which would indicate to the operator that the lubricant in the storage tank should be replenished. However, since many marine propulsion devices have throttles which can be set in a fixed position without being operated by hand, it is important for the protection system to avoid any unintentional increase in engine speed which could result as the lubricant storage tank is being replenished.
It is, therefore, a principal object of this invention to provide an improved engine control system which will protect a two-cycle outboard motor.
It is another object of this invention to provide a protection system for an internal combustion engine which is capable of controlling an operating parameter of the engine in response to a predetermined condition until such time as this control is intentionally terminated.
It is a more specific object of the present invention to provide a protection system for an internal combustion engine which will control the speed of the engine so as to cause a reduction in the engine speed when the lubricant in the storage tank reaches a predetermined level, and maintain the engine speed at a predetermined low level until such time as this control is intentionally terminated.
It is a further object of this invention to provide a protection system which is also capable of controlling the speed of the engine so as to reduce the engine speed in response to an overheat condition.
It is an additional object of this invention to provide a protection system for an internal combustion system which is also capable of providing a plurality of perceptible outputs indicative of the lubricant level and the presence/absence of an overheat condition.
It is yet another object of this invention to provide a protection system for an outboard motor which will maintain an engine control function in response to a low lubricant level, even after the lubricant supply is replenished, until such time as this control is positively disengaged by the operator.
It is yet a further object of this invention to provide a protection system for an internal combustion engine which may be readily and inexpensively interfaced to a capacitive discharge ignition system of the engine to automatically initiate control of the speed and manually release such control over the engine speed.